1. Field of the Invention
The present invention relates to a calibration method and device in an electronic component mounting apparatus for mounting electronic components on substrates or circuit boards. In particular, it relates to a calibration method and device for preventing errors in the mounting position of components when a component placing device replaces another which is different in performance.
2. Discussion of the Related Art
Electronic components that are mounted on circuit boards by electronic component mounting apparatuses of this type include small-type electronic components which are used in a large quantity such as chips and large type electronic components which are used in a small quantity but many in the kinds of shapes or which are needed to be mounted precisely such as ICs having fine leads. Generally, small-type electronic components used in a large quantity are mounted using a high-speed, small component mounting apparatus with a plurality of suction nozzles, whereas large-type electronic components are mounted using a different-shape-component mounting apparatus which is slow in operation speed but has such a flexibility as to deal with various kinds of components and a high accuracy mounting function. Therefore, it has been often the case that a known electronic component mounting line is constructed by arranging a high-speed, small-component mounting apparatus and a different-shape-component mounting apparatus in series. Or, it is has also been practiced that an electronic component mounting line is constructed using a plurality of electronic component mounting apparatus each having both of a high-speed, small-component mounting function and a different-shape-large-component mounting function therein.
However, the ratio at which small electronic components and large electronic components are mounted on circuit boards changes in dependence on the types of the circuit board to be produced. Therefore, in the former method of constructing an electronic component mounting line in a combination of high-speed, small-component mounting apparatuses and different-shape-component mounting apparatuses, the mounting operation of electronic components must be carried out with either one of the electronic component mounting apparatus being lowered in operation efficiency, whereby a problem arises in that it is impossible to build an electronic component mounting line capable of always attaining the maximum productivity. On the other hand, in the latter method of using the electronic component mounting apparatuses each having both of the high-speed, small-component mounting function and the different-shape large-component mounting function, it may take place depending on whether the components to be mounted are small electronic components or large electronic components that each of the electronic component mounting apparatuses would have over-function in some respects than as required. This causes a problem that the cost for the equipment rises to be reflected on an increase in the component mounting cost. Further, new types of components to be mounted on circuit boards are developed day by day, thereby making it impossible to predict the new types at the time of designing the electronic component mounting apparatus. Therefore, in designing electronic component mounting apparatuses, it has to be taken into consideration to deal with more types of components than those present at the time of such designing, which disadvantageously results in redundant or excess equipments thereby increasing the cost for equipments.
On the other hand, as disclosed for example in Japanese unexamined, published patent application No. 7-19816 (1995-19816), there has been proposed a method of building an optimum component mounting line which is capable of meeting the ratio of small components to large components which are mounted on circuit boards to be produced as well as on the types of the components used therein, by making it possible that a component placing device which holds and mounts electronic components can be replaced by the worker with another in a short time at the site where the component mounting line is installed.
In an electronic component mounting apparatus of the type as shown in FIG. 5, a component placing device 26 provided with a component placing head 28 and a board recognizing camera 25 are installed on a movable table 24 that is supported movably in X direction end Y direction with respect to a base frame 11, and a component recognizing camera 15 is fixed on the base frame 11. The electronic component mounting apparatus 10 detects, by the board recognizing camera 25, the position of a board mark Sm provided on the circuit board S that has been loaded, positioned and held by a circuit board transfer device 12, then moves a slide 21 and the movable table 24 respectively in the X and Y directions to perform the position compensation based on the detected position of the board mark Sm and then mounts a component P which has been taken out from a component supply device 13 and has been held at the end of a suction nozzle 29 of a component placing head 28, at a programmed coordinate position on the circuit board S. Further, in the mid course that the component P held at the end of the suction nozzle 29 is moved from the component supply device 13 to the programmed coordinate position on the circuit board S, the feed movement of the suction nozzle 29 is once stopped in alignment with the component recognizing camera 15. Thus, the deviation of the center of the component P from the center line O3 of the suction nozzle 29 (hereinafter also referred to as “suction nozzle center line O3”) is detected by the component recognizing camera 15, so that the feed amounts of the slide 21 and the movable table 24 are compensated for the deviation. In this manner, the component P can be mounted precisely at the programmed target coordinate position on the circuit board S.
In the case that plural component placing devices of different kinds or types are selectively and replaceably installed to the base structure of the mounting apparatus as mentioned earlier, it is required to do a precise calibration for correcting the positional relation between an optical axis O1 of the board recognizing camera 25 (hereinafter referred to as “board camera optical axis O1”) and the center line O3 of the suction nozzle 29 (i.e., the distance X4 in the X-direction and the distance Y4 in the Y-direction as shown in FIG. 1 which shows a part of FIG. 5 in an enlarged scale) after the replacement of the component placing device 26. This calibration is essential to mount the components P precisely at the programmed target positions on the circuit board S. Further, in order to precisely compensate for the deviation of the center of the component P from the center line O3 of the suction nozzle 29, the component P is to be detected by the component recognizing camera 15, with the positional relation between the suction nozzle center line O3 and the optical axis O2 of the component recognizing camera 15 (hereinafter referred to as “component camera optical axis O2”) being grasped correctly.
A method of measuring and calibrating the positional relation (distance X4 and distance Y4) between the optical axis O1 of the board recognizing camera 25 and the center line O3 of the suction nozzle 29 of the component placing device 26 is described as prior art in Japanese unexamined, published patent No. 07-19816. In this method, a component (or a jig, hereinafter the same) held by an suction nozzle is mounted on a circuit board, a board recognizing camera is moved over the component to measure the positional relation between the optical axis of the board recognizing camera and the component, and the positional relation between the optical axis of the board recognizing camera and the center line of the suction nozzle of the component placing device is calibrated based on the measured positional relation and the feed amount and direction of the board recognizing camera. However, there remains a problem that the measuring method involves errors in the shape of the component as well as in the holding position on the suction nozzle.
In the technology disclosed in the Japanese unexamined, published patent No. 07-19816 above, a measuring jig is used which is provided with a first reference mark Gm1 and a second reference mark Gm2 which as references, correspond respectively to a position where the jig is attached to the suction nozzle and another position which the board recognizing camera faces at the same time. In the state that the measuring jig is attached to the suction nozzle with the first reference mark Gm1 being in alignment with the suction nozzle, the first reference mark Gm1 is recognized by a component recognizing camera, and then, the suction nozzle with the measuring jig held thereon is moved relative to the component recognizing camera, so that the second reference mark Gm2 is recognized by the component recognizing camera and then, by the board recognizing camera. Thus, there are gathered the position of the second reference mark recognized by the board recognizing camera, the positions of the first and second reference marks recognized by the component recognizing camera, and the feed distance of the measuring jig. And, the setting position of the board recognizing camera with respect to the suction nozzle is detected based on these gathered data. In this method, since the simple measuring jig only is required to prepare, the setting position of the board recognizing camera with respect to the suction nozzle can be measured sufficiently precisely at a reduced cost for materials required therein. Further, when the measuring jig is held to the suction nozzle, automatic measurement can be done under the control of a control device of the electronic component mounting apparatus or the like, so that an advantage can be obtained in that there can be eliminated errors in measurement which may otherwise be caused in dependence on the degree in skill of the worker.
However, in the method described in the aforementioned Japanese published patent, reference marks are provided at the positions respectively corresponding to the suction nozzle and the board recognizing camera, and thus, the measuring jig made large in size has to be held on the suction nozzle with one of the reference marks being in alignment with the same. This may disadvantageously cause the suction nozzle to be deformed due to the gravity of the measuring jig, thereby resulting in measurement errors, or causes the measuring jig to be detached from the suction nozzle with a small external force. Therefore, problems arise in that it is not easy to practice to measure the setting position of the board recognizing camera relative to the suction nozzle with the measuring jig being held not to be detached from the suction nozzle.